He received a briefing from Homeland Security Adviser John Brennan, White House officials say. Obama then canceled the campaign events to return to Washington to focus on the shooting.

The president felt that suspending the campaign "is the appropriate step ... and today we are focused on remembering the victims and finding out what happened," Obama campaign spokeswoman Jen Psaki said in Florida.

En route to the airport, Obama was briefed again, this time by Brennan and two others - FBI Director Robert Mueller and White House Chief of Staff Jack Lew.

Asked by reporters if the White House plans on new efforts to crack down on gun-related violence, White House Spokesman Jay Carney said: "The president believes we need to take common sense measures that protect the Second Amendment rights of Americans while ensuring that those who should not have guns under existing laws do not get them."

Carney added that the White House does not believe "there was an apparent nexus to terrorism" in the Colorado shootings.

The president spoke to Aurora Mayor Steve Hogan. While traveling to the airport to return to Washington, Obama called Gov. John Hickenlooper.